BAGHDAD, June 23: Militants vowed on Wednesday to assassinate Iraq's interim prime minister, hours after saying they had beheaded a South Korean hostage in the violent run-up to a US handover to Iraqi rule.

Abu Musab al Zarqawi, a Jordanian accused by US officials of organizing many deadly attacks in Iraq and having links to the Al Qaeda, made the threat against Prime Minister Iyad Allawi on a website.

"As for you, Allawi - sorry, the democratically elected prime minister - we have found for you a useful poison and a sure sword," said a taped voice, purported to be Mr Zarqawi's own.

Mr Allawi, a tough former Baathist who plotted against Saddam Hussein from exile, responded defiantly. "We do not care about these threats, we will continue to rebuild Iraq and work for freedom, democracy, justice and peace. Iraqis have faced these threats before," said a spokesman for Iyad Allawi.

The interim government, selected by a UN envoy in consultation with US and Iraqi officials, will be sworn in when the US-led occupation formally ends in a week's time. Mr Zarqawi's group, Jama'at al Tawhid and Jihad, said on Tuesday it had decapitated South Korean hostage Kim Sun-il after Seoul refused to withdraw forces from Iraq.

Hours after finding Kim's body, US forces launched an air strike on a suspected safe house of Zarqawi's group in Falluja, west of Baghdad, the second such raid in four days.

A senior US military official said around 20 foreign fighters were killed in the strike, while Falluja residents said the attack destroyed a garage and killed four people. -Reuters